Climate of the Canadian arctic

M.T. Cranium

I thought some readers of this forum might be interested in the details of the climate of Canada's arctic region.

The Canadian arctic from a climatic perspective is basically the entire region of the arctic islands plus the portion of the mainland north of the tree line which would include the northern third of Yukon, about half of the Northwest Territory, and all of Nunavut on the mainland (the expanse formerly known as Keewatin District), as well as significant portions of northern Manitoba, northern Quebec and Labrador.

The subarctic is defined as a zone with arctic winters (perhaps not quite as long) but temperate summers more typical of the climates further south. In Canada, the subarctic would include most of Yukon, the remainder of the Northwest Territory not in the arctic region, parts of northern Saskatchewan, central-northern Manitoba, parts of northern Ontario adjacent to Hudson and James Bay, and about half of Quebec and most of Labrador excluding a coastal strip south of Hamilton Inlet.

Subarctic (and even arctic) climates can also be found at high elevations quite a bit further south, both in the western mountains, and parts of the eastern Appalachians. The summit of Mount Washington NH has a subarctic climate, and so does the peak of a relatively low mountain (Old Glory Mountain) just a few miles northwest of where I live. The subarctic zone ends at elevations below 1800 metres around here, and 2200 metres in states like Utah and Nevada.

So, to return to the main topic of arctic climate, one major factor that influences it is the six weeks or longer period of darkness that occurs in most of that climate zone, centered on the winter solstice. Winters start very early in the arctic, snow can fall in late August and often starts to cover the ground in September. A snow pack builds up over October to January after which it often stabilizes due to the drier weather conditions of February to April. Temperatures fall to around -10 or -20 C through September and October, and fluctuate in the -20 to -30 range in November, -25 to -35 in December, and often a bit colder than that in January and February. The coldest part of winter is about equally likely to occur in February as in January, and sometimes happens in the first part of March. A spell of clear, calm conditions with temperatures near or below -40 C often provides the winter minimum, and at most locations in the Canadian arctic, that winter minimum averages around -42 to -45 C. A few sheltered locations on the northernmost islands can drop below -50 C as can frost hollows in Yukon although many of those are more in the subarctic climate region. The extremes seen in parts of Siberia are not quite replicated in Canada or Alaska but readings within 5 C deg of Siberian records have been observed (-63 C is the lowest reading in Canada at a location near the Alaska-Yukon border, in Feb 1947).

The first part of the winter sees frequent low pressure areas which often track west to east through the southern part of the arctic region, and each one can drop a few centimetres of snow. In very unusual synoptic patterns, a bit of drizzle or light rain can fall even in December and January, at least south of about 75 N lat. The eastern part of the arctic islands get stronger lows arriving from the south or southeast at times, and can see heavier falls that sometimes become mixed. Winds are often very strong during and after the passage of these lows, as there is nothing on the rocky, rolling landscape to deter the wind. By late January, a more settled pattern dominated by arctic highs (often spawned from either Siberian or Greenland highs) develops, and snowfall drops off. If the location was in polar night darkness, the sun re-appears over the southern horizon for short periods but is too low to warm up the air even slightly, so there is little difference in temperature from night to day until later in March and April when the feeble sun has some effect. The winter would end faster, except that the storm track then returns from the south and creates a brief season that is rather like the autumn with frequent light snowfalls, mixed falls of sleet and snow, and a return to more cloud and strong winds. Except in a few anomalous years, this means that freezing temperatures linger until around mid-June, but by then continual daylight assists in the slow melting of the remnant snow pack, which usually stays about even through most of May and then begins to disappear in late May and early June.

Summer in the Canadian arctic is similar to October weather in southern Canada. There can be some warm and sunny spells, modified near open water by fog and low cloud. There can also be frequent unsettled spells and occasional strong winds. The storm track tends to move as far north as the 75-80 N zone, and strong westerly winds are frequent. Frontal passages can be intense with hail and damaging wind gusts (damaging to human structures), although thunder is rare in the arctic region (quite frequent in the subarctic however). Snow can fall at any time although in most years, July is free from snow as are late June and early August. Frosts can occur as early as late July or early August, as soon as some darkness begins to return at night (or even with a low sun above the horizon at midnight).

Typical mean temperatures in the arctic islands are around -32 to -35 C in the coldest months and 5-10 C in the warmest months. July is almost always the warmest month although some years have nearly equal values in August and a few have seen a peak in either June or August. Readings of about 23-26 C are considered extremely warm in the arctic, and closer to the northern limit of the islands, 20 C is unusual. Spells of a few days of those temperatures can occur but not every summer.

There is a lot of variability from year to year especially in summer. Some years hardly have a summer at all, with a lot of low cloud, mixed sleety precip, and temperatures barely above freezing. Others have a fairly decent summer. Those years are usually when the ice in the Northwest Passage disappears and ordinary sailing vessels can navigate through, but it's not a sure thing and prospective travels through the NWP have been impossible in some recent summers.

From the rather sparse data available, it appears that the Canadian arctic is now about 2 to 3 C deg warmer than it was in the mid-20th century. The most noticeable difference in the climate is that the season of thaw is somewhat longer at either end. The peak of summer and the longer depth of winter have not changed all that much. You do see in the records a few more anomalous warming intrusion events. From the even more limited understanding we have of the 19th century colder climate era up north, the overall difference is probably now in the order of 3 to 4 C deg. Almost every summer, the NWP remained frozen in that era. Longer term climate investigations have revealed that less sea ice occurred at some points in the post-glacial era, allowing Inuit hunters to survive on whale hunting in regions of the central arctic islands where the whales are not that common even nowadays. Both the Medieval Warm Period and the Neolithic (up to around 1500 BC) are suspected of having this more moderate climate.

The subarctic climates blend most of those details with more ordinary summer statistics. Temperatures can easily reach 30 C or higher in subarctic climates. Summer includes most of June and August as well as July, and May and September are more moderate and transitional months. The typical subarctic climate has snow cover from mid to late October, lasting to late April or early May. Lakes in subarctic Canada can remain frozen to early July.

Hudson Bay is a major factor in positioning climate boundaries. If Hudson Bay was not there, the subarctic climate's southern boundary would likely extend across its central region instead of dropping down to surround all of its shorelines. Hudson Bay while an extension of the Atlantic Ocean is relatively low in salt content and freezes from about early December to late June in most seasons. James Bay, its southern extension, has almost as long a freeze.

If you wish to see a more in-depth probe of arctic Canada climate variations I have a thread in the climate change forum of Net-weather with all those details. In this thread I could perhaps answer any less detailed questions.

The comparison of the Canadian arctic to the Russian arctic or the Svalbard region is that they see somewhat more moderate winter temperatures as there is open water closer to the arctic regions, and a more active storm track. There is more similarity further east in northern coastal Siberia. Climates inland in Siberia are very similar to those in subarctic Canada, while perhaps a bit more extreme. Greenland's coastal regions have a somewhat more moderate version of the Canadian arctic climate, but the height of the Greenland ice cap means hat its average temperatures are generally lower than the central Canadian arctic even though most of the central arctic islands are not much elevated above sea level.

(for reference, Baffin Island's north coast has high mountains and some permanent ice, also Devon, Ellesmere and Axel Heiberg Islands have some extensive ice caps. The rest of the arctic islands and the arctic mainland regions have no remaining permanent ice but can have seasonal snow fields depending on depths the previous winter. Only a few parts of Victoria Island are much higher than 300 metres, but snow is seen on those higher hills at times in July. Islands further north have some small ice fields too. The landscape of the mainland portion of the arctic consists of many lakes of various sizes, barren rock, but few hills of any great height except in northern Labrador, and those hills are partly ice covered. Northern Quebec has generally fewer lakes than the zone west of Hudson Bay.)